How the vegetarian diet influences recreational and professional athletes' physical performance: A systematic review
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Research, Society and Development, v. 10, n. 9, e26910917952, 2021
(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
How the vegetarian diet influences recreational and professional athletes’ physical
performance: A systematic review
Como a dieta vegetariana influencia o desempenho físico de atletas recreativos e profissionais: Uma
revisão sistemática
Cómo influye la dieta vegetariana en el rendimiento físico de lo atletas recreativos y profesionales:
Una revisión sistemática
Received: 07/06/2021 | Reviewed: 07/15/2021 | Accept: 07/17/2021 | Published: 07/25/2021
Marina Nascimento de Araújo
ORCID: https://orcid.org/0000-0002-3488-580X
Universidade Federal do Rio de Janeiro, Brazil
E-mail: marinaufrj@icloud.com
Alexandre Palma
ORCID: https://orcid.org/0000-0002-4679-9191
Universidade Federal do Rio de Janeiro, Brazil
E-mail: palma_alexandre@yahoo.com.br
Paula Guedes Cocate
ORCID: https://orcid.org/0000-0003-1208-6481
Universidade Federal do Rio de Janeiro, Brazil
E-mail: paulacocate@gmail.com
Abstract
Vegetarianism has been getting increasing attention over the years, in society in general and in sport in particular.
However, the growth in the number of people following a meatless diet notwithstanding, vegetarianism should be
practiced with caution, especially by professional and recreational athletes, considering the possible lack of certain
nutrients and decline in their physical performance. Therefore, the present review aimed to determine whether
following a vegetarian diet influences recreational and professional athletes’ physical and sports performance. A
search of the databases Medline/Pubmed, Scopus, Web of Science, and Lilacs gave 343 relevant articles; however,
only 15 of these focused on the vegetarian diet and physical performance, in accordance with the inclusion criteria.
These studies compared the vegetarian diet with the omnivorous diet, and found that it did not negatively influence
physical performance. Moreover, those who followed a vegetarian diet seemed to have a higher volume of maximum
oxygen (V̇O2 max), which positively influenced their performance. In conclusion, following a plant-based diet does
not seem to harm recreational and professional athletes.
Keywords: Adults; Vegetarian diet; Physical and sports performance.
Resumo
O vegetarianismo tem recebido atenção crescente ao longo dos anos, na sociedade em geral e no esporte em particular.
Contudo, apesar do crescimento do número de pessoas que seguem uma dieta sem carne, o vegetarianismo deve ser
praticado com cautela, principalmente por atletas profissionais e recreativos, considerando a possível falta de alguns
nutrientes e declínio no desempenho físico. Portanto, a presente revisão teve como objetivo determinar se seguir uma
dieta vegetariana influencia o desempenho físico e esportivo de atletas recreativos e profissionais. Uma busca nas
bases de dados Medline / Pubmed, Scopus, Web of Science e Lilacs resultou em 343 artigos relevantes; no entanto,
apenas 15 desses enfocavam a dieta vegetariana e desempenho físico, de acordo com os critérios de inclusão. Esses
estudos compararam a dieta vegetariana com a dieta onívora e descobriram que ela não influenciava negativamente o
desempenho físico. Além disso, quem seguia dieta vegetariana parecia ter maior consumo máximo de oxigênio (V̇O2
max), o que influenciava positivamente em seu desempenho. Em conclusão, seguir uma dieta baseada em vegetais não
parece prejudicar os atletas recreativos e profissionais.
Palavras-chave: Adultos; Dieta vegetariana; Rendimento físico-esportivo.
Resumen
El vegetarianismo ha recibido una atención cada vez mayor a lo largo de los años, en la sociedad en general y en el
deporte en particular. Sin embargo, a pesar del crecimiento en el número de personas que siguen una dieta sin carne,
el vegetarianismo debe practicarse con precaución, especialmente por parte de los atletas profesionales y recreativos,
considerando la posible falta de ciertos nutrientes y la disminución de su rendimiento físico. Por lo tanto, la presente
revisión tuvo como objetivo determinar si seguir una dieta vegetariana influye en el rendimiento físico y deportivo de
1Research, Society and Development, v. 10, n. 9, e26910917952, 2021
(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
los atletas recreativos y profesionales. Una búsqueda en las bases de datos Medline / Pubmed, Scopus, Web of
Science y Lilacs arrojó 343 artículos relevantes; sin embargo, solo 15 de ellos se enfocaron en la dieta vegetariana y el
rendimiento físico, de acuerdo con los criterios de inclusión. Estos estudios compararon la dieta vegetariana con la
dieta omnívora y encontraron que no influyó negativamente en el rendimiento físico. Además, los que siguieron una
dieta vegetariana parecían tener un mayor volumen de oxígeno máximo (VO 2 máx.), Lo que influyó positivamente en
su rendimiento. En conclusión, seguir una dieta a base de plantas no parece perjudicar a los deportistas recreativos y
profesionales.
Palabras clave: Adultos; Dieta vegetariana; Rendimiento físico y deportivo.
1. Introduction
Vegetarianism has been receiving increasing attention worldwide; as a result, the number of people practicing it has
increased over the years. Approximately 22% of the world’s population is vegetarian, while 8% of elite athletes are vegetarian
(Collins et al. 2020).
The Brazilian Vegetarian Society (2017) considers vegetarianism as the dietary regime that excludes all types of meat
and may, in some categories, include animal derivatives. However, the vegetarian diet can be classified in different ways,
depending on the inclusion or exclusion of certain animal products. In this sense, a vegetarian can be categorized under one of
the following four classifications: “ovolactovegetarian”—those who consume eggs and dairy products; “lactovegetarian”—
those who consume dairy products but not eggs; “ovovegetarian”—those who consume eggs but not dairy products; or “strict
vegetarian”—those who do not consume any animal products or ingredients such as gelatin, albumin, milk proteins, some
dyes, and thickeners (Slywitch 2012). Moreover, according to the definition provided by the Vegan Society. (n.d.), vegans are
also considered strict vegetarians in terms of diet. In addition to diet, veganism is a philosophy of life that tries to exclude all
things related to animal exploitation, including food, cosmetics, and clothing.
While there are several reasons motivating individuals to become vegetarians, such as religiosity, sustainability,
moral beliefs, and being against different treatment in relation to other species; however, according to Courceiro et al. (2008),
health seems to be the most common reason. Some studies have associated the vegetarian diets with a lower risk of
cardiovascular and metabolic diseases (Orlich et al. 2013; Kim et al. 2019; Qian et al. 2019). Moreover, a balanced vegetarian
diet is associated with a higher intake of complex carbohydrates, fiber, fruits, vegetables, antioxidants, phytochemicals, and a
lower intake of saturated fat and cholesterol, when compared with the omnivorous diet (Ada 2003; Rauma & Mykkanen 2000;
Huang et al. 1999). Conversely, the general population still believes that a diet devoid of animal products may be associated
with poor performance due to the lack of certain nutrients, such as protein, creatine, vitamin B12, and vitamin D (Fields et al.
2016; Solis et al. 2017).
According to the American College of Sports Medicine (2016), “the performance of, and recovery from, sporting
activities are enhanced by well-chosen nutrition strategies” (p. 543). Therefore, the nutritional aspect must be considered as an
important factor for recreational athletes’ and professional athletes’ physical and sports performance. The American Dietetic
Association (2003) argues that vegetarianism and veganism are suitable for different groups of people such as pregnant
women, nursing mothers, children, adolescents, adults, and even athletes. However, even in a balanced vegetarian diet, which
is considered appropriate for maintaining health throughout one’s life cycle (Craig & Mangels 2009), attention should be paid
to nutritional adequacy vis-à-vis physical performance in professional and recreational athletes, as many of their necessary and
desirable nutritional needs may remain unmet, leading to a decline in performance.
Considering the increasing adherence to plant-based diets, without meat consumption and with regular physical
exercise, this systematic literature review aimed to determine whether following a vegetarian diet influences recreational
athletes’ and professional athletes’ physical and sports performance.
2Research, Society and Development, v. 10, n. 9, e26910917952, 2021
(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
2. Methodology
Eligibility criteria
The research strategy was defined based on the question “Does following a vegetarian diet influence recreational
athletes’ and professional athletes’ physical and sports performance?” and considered the PICO (Guyatt et al. 2008)
(Population; Intervention; Comparison; Outcome) components.
Population: adults or the elderly
Intervention: vegetarian diet
Comparison: not following a vegetarian diet
Outcome: increase or decrease in physical and sports performance
All observational studies that sought to identify the effects if vegetarian diets on physical and sports performance
were considered eligible. Publications such as letters to the editor, editorials, literature reviews, meta-analyses, and points of
view were excluded.
Search sources and strategies
The databases searched were Medline/Pubmed, Scopus, Web of Science, and Lilacs by employing independent search
strategies. The references of the eligible articles were checked to select studies of interest. The search strategies using
keywords, other terms, and Boolean language are described in Table 1, which was conducted in accordance with the guideline
described by the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) (Liberati et al, 2009).
Table 1. Search Strategies in different bases
Base Strategie Data of the last Result
research
Medline/ Pubmed ((Adult[MeSH] OR Adult[TiAb] OR athletes[MeSH] OR athlete*[TiAb] OR
“practicing sports”[TiAb] OR “practicing physical activities”[TiAb]) AND 04/19/2021
(“Diet, Vegetarian”[MeSH] OR vegetarian[TiAb] OR vegan[TiAb] OR “energy
76
restricted diets” [TiAb]) AND (“Athletic Performance”[MeSH] OR “Athletic
Performance “[TiAb] OR “Sports performance”[TiAb] OR “physical
performance”[TiAb] OR OR performance”[TiAb]))
Scopus (TITLE-ABS-KEY (adult* OR athlete* OR "practicing sports" OR "practicing
physical activities") AND TITLE-ABS-KEY ("Diet, Vegetarian" OR vegetarian 04/19/2021
OR vegan OR "energy restricted diets") AND TITLE-ABS-KEY ("Athletic
186
Performance" OR "Sports performance" OR "physical performance" OR
performance))
Web of Science (Adult* OR athlete* OR “practicing sports” OR “practicing physical activities”)
AND TÓPICO: (“Diet, Vegetarian” OR vegetarian OR vegan OR “energy 04/19/2021
restricted diets”) AND TÓPICO: (“Athletic Performance” OR “Sports
79
performance” OR “physical performance” OR performance)
Lilacs (atleta OR atletas OR esporte OR esportes OR "atividade física") AND
(vegetariana OR vegetariano OR vegan OR vegetarianas OR vegetarianos OR 04/19/2021
veganos OR "dieta com restrição de energia") AND (performance)
2
Total 343
Source: Authors.
Risk of bias
After the articles were selected, duplicate records were removed. Subsequently, the three authors selected the articles
independently, starting with the title. The reviewers then analyzed the articles, and disagreements were resolved in accordance
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(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
with all authors. Thereafter, the three authors read the abstracts of the selected articles and independently selected the eligible
ones, thus ensuring greater accuracy. Disagreements were resolved by consensus, and the eligible articles were then read in
full.
3. Results
Article selection
The initial search yielded 343 articles, of which 15 were selected after following all the steps. Figure 1 shows the
entire process.
Figure 1. Flowchart diagram of bibliographic research according to Preferred Reporting Items for Systematic Review and
Meta-Analysis (PRISMA) guidelines
Source: Authors.
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Summary of results
Among the 15 articles, one (5.6%) reported that the vegetarian diet negatively influences physical and sports
performance, while eight (44.4%) reported the opposite, and nine (50%) reported that the diet had no influence on the physical
and sports performance (the abovementioned percentages were obtained by considering a total of 18 results in the 15 articles as
three articles presented more than one result and, thus, were mentioned in different tables; consequently, these articles had to
be counted twice). The studies in which the diet worsened performance, or which showed a negative association between the
two are presented in Table 2; those in which the diet improved performance, or which showed a positive association between
the two are presented in Table 3; and those in which the diet had no effect on performance, or which showed no association
between the two are presented in Table 4.
Table 2. List of the studies included in the review in which the diet worsened performance, or which showed a negative
association between the two (author name, year, aim, sample characteristics, study design and main results)
Reference Aim Sample Design Main Results
*Hebbelinck et To assess average daily dietary Size: 44 Type: Cohort- The results of the physical
al. (1999) intakes of energy in vegetarian study fitness tests in the present study
children, adolescents, and young Gender: 31 females and 13 indicate that in the 3 strength
adults and included males related tests, ie, hand grip
determination of height and strength (static strength),
Intervention: 44
weight; triceps, suprailiac, and standing long jump (explosive
Lactoovovegetarians for ≥3
calf skinfold thicknesses; puberty strength), and 30-s sit-up
years
ratings; and physical fitness. (abdominal strength), the
Control group: Dutch nutrient vegetarian subjects scored at or
database below the average level of
performance of their respective
Recreational athletes: 44 reference age groups.
Age group: 20 to 22 years
Physical method: Strength;
cardiorespiratory endurance.
Country: United States
Legend: a) Professional athletes are professional competitors, federates. While, recreational athletes do not necessarily participate in
competitions. b) * The study by Hebbelinck et al. (1999) identifies contrasting results that can be applied to other tables. There was a
negative influence in relation to vegetarian participants in the strength tests, but there was no negative association in relation to the aerobic
test for vegetarians in the same study, which can be seen in Table 3. Source: Authors.
5Research, Society and Development, v. 10, n. 9, e26910917952, 2021
(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
Table 3. List of the studies included in the review in which the diet improved performance, or which showed a positive
association between the two (author name, year, aim, sample characteristics, study design and main results)
Reference Aim Sample Design Main Results
*Lynch et al. To compare elite vegetarian Size: 70 Type: Cross- V̇O2 max differed for females by
(2016) and omnivore adult endurance sectional study diet group (53.0; sd=6.9 and 47.1;
Gender: 30 females and 40
athletes for maximal oxygen sd= 8.6 mL/kg/min for vegetarians
males
uptake (V̇O2máx) and strength and omnivorous respectively, p <
Intervention: 27 Vegans for ≥2 0.05).
years
Control group: 43 omnivores
Professional athletes: 70
Age group: 21 to 58 years
Physical method: V̇O2 max;
peak torque for leg extensions
Country: Switzerland
Mujika To report on the performance Size: 1 Type: Case The lacto-ovo vegetarian athlete
(2018) outcomes and subjective study used a LCHF diet, maintaining his
Gender: male
assessments of long-term low vegetarian eating pattern, for 32
carbohydrate, high fat (LCHF) Intervention: (LCHF) diet for 32 weeks. Within those 32 weeks, his
diet in a world-class long- weeks performance declined. He regained
distance triathlete. Control group: Lacto-ovo his usual level of performance
vegetarian within 5 weeks of being back on a
high-carbohydrate lacto-ovo
Professional athletes: 1 vegetarian diet.
Age group: 39 years
Physical method: Marathon;
ultramarathon
Country: United States
Veleba et al. To compare the effects of a Size: 74 Type: Maximal oxygen consumption
(2016) vegetarian and conventional Randomized (V̇O2máx) increased by 12% in
Gender: 39 females and 35
diet with the same caloric controlled vegetarian group, whereas no
males
restriction on physical fitness study significant change was observed in
and resting energy Intervention: 37 Vegetarians conventional diet.
expenditure after 12 weeks of Control group: 37 Conventional Watt max increased by 21% in
diet plus aerobic exercise in Hiphocaloric Diet vegetarians, whereas it did not
patients with type 2 diabetes
Recreational athletes: 74 change in conventional diet.
(T2D).
Ill: 74
Illness: Type 2 Diabetes
Age group: –
Physical method: V̇O2máx;
maximal performance (Watt
max)
Country: Switzerland
6Research, Society and Development, v. 10, n. 9, e26910917952, 2021
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*Hebbelinck To assess average daily Size: 44 vegetarians Type: Cohort- Both the vegetarian male and
et al. (1999) dietary intakes of energy in study young adults performed better in the
Gender: 31 females and 13
vegetarian children, step test than did the reference
males
adolescents, and young adults group. This latter finding suggests
and included determination of Intervention: 44 that the vegetarian subjects had
height and weight; triceps, Lactoovovegetarians for ≥3 better cardiorespiratory endurance.
suprailiac, and calf skinfold years
thicknesses; puberty ratings; Control group: Dutch nutrient
and physical fitness. database
Recreational athletes: 44
Age group: 20 to 22 years
Physical method: Strength and
cardiorespiratory endurance.
Country: United States
Leischik e To present the findings of an Size: 11 Type: Case In terms of performance
Spelsberg ultra-triathlete living on a raw report diagnostics, the vegan athlete
Gender: 11 Females
(2014) vegan diet and having finished showed comparable V̇O2max, V̇O2
the competitions under these Intervention: 1 Raw vegan for 6 at the ventilatory anaerobic
nutritional conditions. years threshold, and %V̇O2 max at
Control group: 10 Mixed diet ventilatory anaerobic threshold
values as compared with the control
Professional athletes: 11 group . V̇O2 and %V̇O2 max at
Age group: 47 to 48 years respiratory compensation point were
somewhat higher for the vegan
Physical method: Maximum athlete. The maximum ergometric
ergometric performance; VO2; performance is higher for the vegan
%VO2max; VO2 at the athlete in absolute terms.
ventilatory anaerobic threshold
(VAT); VO2 at respiratory
compensation point (RCP)
Country: United States
Gazanni et al. To assess the association Size: 223 Type: Case- As the main outcome measure was
(2019) between protein intake and control study used the 6-min walking test and the
Gender: 127 Females and 96
physical performance in a distance walked in metres. Their
males
general population sample. mean vegetable and animal proteins
Intervention: Linear regression intake for gram/kg of body
of 6-min walking test (6MWD) weight/day were, respectively, 0.4
against nutrient intakes for an and 0.7. After adjusting for all the
increase of 10 g/day vegetable potential confounders, there was a
protein significant increase of 20.0 m in the
Control group: Linear distance walked for an increase in
regression of 6-min walking test 10 g/day of vegetable proteins and
(6MWD) against nutrient non-significant variations of −1.8m
intakes for an increase of 10 for an increase in 10 g/day of
g/day animal protein animal proteins and of 0.5 for an
increase in 10 g/day of total
Professional athletes: 115 proteins. The result suggests a
Recreational athletes: 108 positive role of vegetable proteins
on physical performance.
Age group: 45.8 sd = 9.6 years
Physical method: Global
analisys of the
cardiorespiratory; metabolic
system
Country: Sweden
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Król et al. To assess the differences in Size: 52 Type: Case- Vegans displayed a higher V̇O2max
(2020) the athletes’ heart morphology control study x (54.08 vs. 50.10 mL/kg/min, p <
Gender: –
and function and the 0.05).
correlation of these with Intervention: 22 Vegans
The vegans presented a more
dietary habits. Control group: 30 Omnivores eccentric form of remodelling with
Recreational athletes: 52 greater left ventricular end diastolic
diameter (LVEDd, 2.93 vs. 2.81
Age group: > 18 years cm/m2, p = 0.04) and a lower
Physical method: VO2max; relative wall thickness (RWT, 0.39
heart functions vs. 0.42, p = 0.04) and left
ventricular mass (LVM, 190 vs. 210
Country: Sweden g, p = 0.01).
The results demonstrate that
following a plant-based diet does
not impair amateur athletes’
performance and influences both
morphological and functional heart
remodelling.
*Boutros et To examine endurance and Size: 56 Type: Case- Vegans had a significantly higher
al. (2020) muscle strength differences control study estimated V̇O2max and submaximal
Gender: Female
between vegan and omnivore endurance time to exhaustion
participants. Intervention: 28 Vegans for ≥ 2 compared with omnivores.
years
Control group: 28 Omnivores
Recreational athletes: 56
Age group: 25.6 sd= 4.1 years
Physical method: VO2 max;
70% of VO2 max; muscle
strength
Country: England
Legend: a) Professional athletes are professional competitors, federates. While, recreational athletes do not necessarily participate in
competitions. b) * The studies identify contrasting results that could be applied to other tables. c) The study by Lynch et al. (2016)
demonstrate a difference in the maximum V̇O2 variable for women, nevertheless there was no such difference for males in the study. d)
Boutros et al. (2020) verify a difference in the variable of maximum V̇O2 and submaximal endurance time to exhaustion, however there were
no significant differences in relation to the other variables. The other results of the articles could be seen in Table 4. Source: Authors.
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Table 4. List of the studies included in the review in which the diet had no effect on performance, or which showed no
association between the two (author name, year, aim, sample characteristics, study design and main results).
Reference Aim Sample Design Main Results
* Lynch et To compare elite Size: 70 Type: Cross- V̇O2max did not differ for males
al. (2016) vegetarian and sectional study by diet group. Peak torque did
Gender: 30 females and 40 males
omnivore adult not differ significantly between
endurance athletes for Intervention: 27 Vegans for ≥2 years diet groups.
maximal oxygen uptake Control group: 43 omnivores
(V̇O2máx) and strength.
Professional athletes: 70
Age group: 21 to 58 years
Physical method: V̇O2 max; peak torque
for leg extensions
Country: Switzerland
Raben et al. The effect of a lacto-ovo Size: 8 Type: Cross- 6 weeks on a lacto-ovo
(1992) vegetarian and a mixed, over study vegetarian diet caused a minor
Gender: Male
meat-rich diet on the decrease in total testosterone
level of serum sex Intervention: Lacto-ovo vegetarian and no significant changes in
hormones, Control group: Mixed diet physical performance in male
gonadotropins, and endurance athletes compared
endurance performance. Recreational athletes: 8 with 6 wk on a mixed, meat rich
Age group: 21 to 28 years diet.
Physical method: –
Country: United States
Nebl et al. To compare the Size: 76 Type: Cross- The groups showed comparable
(2019) exercise capacity of sectional study training habits in terms of
Gender: 47 Females and 29 Males
vegan, lacto-ovo training frequency, time and
vegetarian and Intervention: 24 Vegans; 26 Lacto-ovo running distance. Moreover,
omnivorous recreational vegetarians similar maximum power output
runners. Control group: 26 Omnivores was observed in all three groups
and no differences regarding
Recreational athletes: 76 arterial lactate throughout the
Age group: 18 to 35 years exercise test and maximum
lactate could be observed
Physical method: Maximum power between the groups.
output; arterial lactate; maximum lactate
Country: United States
Burke et al. To compare changes in Size: 42 Type: All participants followed the
(2008) muscle insulin-like Randomized same high-volume, heavy-load
Gender: 18 Females and 24 Males
growth factor-I (IGF-I) control study resistance-exercise-training
content resulting from Type of Diet: 18 lacto-ovo vegetarians or program for 8 weeks. Creatine
resistance-exercise vegan for ≥ 3 years and 24 Mixed diet supplementation during
training and creatine Intervention: 22 Creatine supplementation resistance-exercise training
supplementation. increases intramuscular IGF-I
Control group: 20 Isocaloric placebo concentration in healthy men
Recreational athletes: 43 and women, independent of
habitual dietary routine.
Age group: 31 to 24 years
Physical method: >70% 1RM
Country: United States
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Novakova To assess the plasma Size: 24 Type: Case- Exercise capacity and maximal
et al. (2016) and skeletal muscle control study oxygen uptake were not
Gender: Male
carnitine content and different between vegetarians
physical performance of Intervention: 16 Vegetarians for ≥ 1.5 and omnivores. Sub-maximal
male vegetarians and years with oral supplementation of 2 g l- exercise (75 % VO2max for 1
matched omnivores carnitine h) revealed no significant
under basal conditions Control group: 8 Omnivores with oral differences between vegetarians
and after l-carnitine supplementation of 2 g l-carnitine and omnivores.
supplementation. Supplementation with l-
Recreational athletes: 24 carnitine significantly increased
Age group: 26 to 31 years the total plasma carnitine
concentration (24 % in
Physical method: V̇O2 max; 75 % omnivores, 31 % in vegetarians)
VO2max and the muscle carnitine content
Country: Germany in vegetarians (13 %).
Vegetarians had maintained
skeletal muscle carnitine stores
despite lower plasma carnitine
concentrations than omnivores.
Baguet et To investigate the Size: 19 Type: There was a significant diet 9
al. (2011) effects of 5 weeks sprint Randomized trainings interaction in soleus
Gender: 9 Females and 10 Males
training combined with control study carnosine content, which was
a vegetarian or mixed Intervention: 9 subjects were allocated to non-significantly increased with
diet on muscle a vegetarian diet mixed diet and non-significantly
carnosine, carnosine Control group: 10 subjects were allocted decreased with vegetarian diet.
synthase mRNA to a mixed diet Carnosine content in other
expression and muscle muscles and gastrocnemius
buffering capacity. Recreational athletes: 20 buffer capacity were not
Age group: 16 to 30 years influenced by training. The
performance during the repeated
Physical method: sprint training program; sprint ability test improved by
Resistance was set to 7 and 8% of the training, without difference
bodyweight for females and males, between groups.
respectively
Both groups were supplemented
Country: Germany with 1 g/day of creatine
monohydrate for 5 weeks.
Shomrat et To determine the effect Size: 24 Type: Clinical Vegetarians and meat-eaters
al. (2000) of creatine feeding on trial respond to creatine feedings
Gender: Male
maximal exercise with similar increases in mean
performance in Intervention: 7 vegetarians and 9 meat- power output during short-term,
vegetarians. eaters ingesting creatine supplemetation maximal exercise.
for 1 week
Control group: 8 Meat- eaters ingesting
glucose for 1 week
Recreational athletes: 24
Age group: 25 to 32 years
Physical method: Peak power output
Country: Germany
Davey et al. To report the process of Size: 1 Type: Case All physical analysis indicated
(2021) an elite male Gaelic study that with adequate knowledge
Gender: Male
football player and education, and appropriate
transitioning from an Intervetion: Vegan diet for 1 year planning, commitment and
omnivorous diet to a Control group: Omnivore iterative feedback, the athlete
vegan diet at the was able to meet nutrition
beginning of a Professional athletes: 1 targets on a vegan diet without
competitive season. Age group: 25 years compromising key performance
indicators compared to the
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Physical method: running performance omnivorous diet of the previous
during match-play season.
Country: Switzerland
*Boutros et To examine endurance Size: 56 Type: Case- Both groups, vegans and
al. (2020) and muscle strength control study omnivores, were comparable in
Gender: Female
differences between terms of strength levels in the
vegan and omnivore Intervention: 28 Vegans for ≥ 2 years upper and lower body muscles.
participants. Control group: 28 Omnivores
Recreational athletes: 56
Age group: 25.6 sd= 4.1 years
Physical method: VO2 max; 70% of VO2
max; muscle strength
Country: England
Legend: a) Professional athletes are professional competitors, federates. While, recreational athletes do not necessarily participate in
competitions. b) * The studies identify contrasting results that could be applied to other tables. Source: Authors.
4. Discussion
Only one study showed that the vegetarian diet had a negative influence on athletes’ physical performance.
Hebbelinck et al. (1999) initiated the use of strength tests to evaluate performance: a hand grip strength test (static strength), a
standing long jump test (explosive strength), and abdominal flexion (abdominal strength) test, and found that the performance
of the vegetarian participants was poorer than that of those in the control group, the daily energy intake of the vegetarians was
significantly lower than that of the omnivores, which could explain the significant difference observed in the strength test
performance of the two groups. Thus, each type of exercise and diet requires a different dietary regime to fulfill the energy
requirements necessary for optimum performance. Conversely, Boutros et al. (2020) performed the
one repetition maximum (1RM) test for upper and lower limbs to analyze muscle strength in vegetarians and omnivores, and
found no significant difference between the two groups. It is worth noting that of the 15 studies reviewed, strength tests had
been conducted as an analysis resource in only five articles in the present analyze.
Considering that strength athletes have specific needs when it comes to training and nutrients in their diet, future
studies should investigate the association between resistance exercises and the vegetarian diet, thus expanding the literature on
the topic, which is currently scarce.
In this review, studies indicating that the vegetarian diet is beneficial for performance had conducted aerobic tests to
analyze performance, and in most of these, the participants were endurance athletes. Gazanni et al. (2019) evaluated their
participants in the short term through only the diets suggested as part of their investigation; furthermore, Veleba et al. (2016)
randomly distributed their study participants into a control group and vegetarian group, including the diets suggested only in
the investigation.
According to Nieman (1998), vegetarian diets usually have higher levels of carbohydrates, which can be beneficial for
endurance athletes as they enhance the body’s glycogen reserves, thereby improving performance. Some studies present in this
review that showed a positive correlation between the vegetarian diet without supplementation and with aerobic performance,
reported an increase in V̇O2 max and vagal cardiac activity, which suggests several benefits for the cardiovascular system of
these athletes. Nonetheless, some of these studies possess limitations, such as different levels of physical conditioning and
uncontrolled diet. Furthermore, Mujika (2019) observed an improvement in the performance of the athletes under analysis in
endurance tests using a vegetarian diet, compared with a low-carbohydrate and high-fat diet, however, some questions remain
11Research, Society and Development, v. 10, n. 9, e26910917952, 2021
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unanswered, as food was the only factor analyzed, and other internal and external variables may have interfered with the
athlete’s performance.
Only one of the studies reviewed had participants with chronic disease, Veleba et al. (2016) enrolled only diabetics,
and after following the vegetarian diet along with aerobic exercise, they showed lower visceral fat levels, which may suggest a
decrease in muscle fat, indicating a positive association with physical conditioning; the authors also reported a correlation
between lower intracellular fat rates in vegetarians and increased insulin sensitivity, and an increase in metabolic flexibility
was also observed, indicating a possible correlation between metabolic flexibility and V̇O2 max. According to Olfert and
Wattick (2018), diets devoid of animal products, prioritizing whole grains, fruits, vegetables, legumes, and nuts, and low in
saturated and trans-fat, which can be characterized as vegetarian diets, are associated with a lower risk of metabolic diseases
such as diabetes, and provide physical benefits to patients.
Other studies showed that the vegetarian diet had no influence on performance. In most, the common analysis
resource used was the blood test associated with performance tests; variables such as skeletal muscle carnitine content and
creatine supplementation were analyzed. Furthermore, the study by Baguet et al. (2011) included omnivorous participants who
only after a five-week intervention were able to follow a diet devoid of animal products.
Some of the studies in which the vegetarian diet did not influence physical and sports performance investigated the
respective influences of creatine and carnosine on anaerobic activities. According to Barr et al. (2004), creatine is found mainly
in poultry, fish, and meat, and is synthesized endogenously; its highest concentration is in the muscle, mainly in the form of
phosphocreatine. During exercise, phosphocreatine breaks down to generate energy to resynthesize adenosine triphosphate
(ATP). Thus, a high concentration of creatine can prolong the exercise’s supra-maximal intensity or shorten the recovery time.
Subsequently, Burke et al. (2008) showed that omnivores have higher levels of creatine. However, vegetarians,
because they have lower levels of it, seem to be more receptive to the supplementation of this amino acid and absorb it more,
having similar adaptations, and without any impact on athletes who wish to follow this type of a plant-based diet. Shomrat et
al. (2000) too conducted a study with creatine supplementation among vegetarians and omnivores, comparing peak and
average potency during the Wingate test, found lower creatine levels in vegetarians; however, potency during the test was not
significantly affected after supplementation, both groups increased their average potency, but only omnivores increased their
peak potency. In contrast to the studies analyzed in the present review, Barr et al. (2004) showed a significantly higher increase
in total muscle creatine, lean mass, and better performance in knee flexion and extension among vegetarians after
supplementation, suggesting that vegetarian athletes who supplement creatine and participate in sports requiring the
ATP/phosphocreatine system may show better results than omnivores.
Almannai et al. (2019) reported that one of the fundamental functions of carnitine is to produce cellular energy. It is
primarily found in animal protein and dairy products, which is favorable to omnivores, who absorb it in greater amounts
through food. Vegetarians, on the other hand, obtain carnitine mainly through endogenous synthesis.
Novakova et al. (2016) compared body carnitine reserves and physical performance in people following diets with
and without animal protein. Although vegetarians had lower plasma carnitine levels, carnitine reserves in skeletal muscle were
similar between the two groups. Furthermore, although L-carnitine supplementation led to a slight increase in muscle carnitine,
skeletal muscle function and energy metabolism were not affected; thus, performance results did not differ between the groups.
5. Conclusion
In conclusion, the present review indicates that there is no consensus on the topic in the literature. However, it should
be noted that only one study, which used strength tests to analyze performance, showed that the vegetarian diet worsened
12Research, Society and Development, v. 10, n. 9, e26910917952, 2021
(CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i9.17952
physical and sports performance. To date, few studies have investigated vegetarian diets using strength tests. Moreover, a
significant number of those reviewed found that the vegetarian diet had a positive influence on performance, noting a possible
improvement in the cardiorespiratory system of the participants engaging in aerobic activities; while others showed that a diet
devoid of animal products did not influence recreational and professional athletes’ performance many of the variables analyzed
had even values, and in the variables in which a difference was observed, such as creatine levels, supplementation was found to
reduce such deficiencies.
For future researchers and works, it would be interesting to analyze larger samples of groups considered vegetarian
and greater attention to physical methods, such as V̇O2 max and muscle strength is encouraged. In addition, a better leveling of
participants in terms of physical conditioning and dietary monitoring will be beneficial.
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